Conventional internal combustion engines of the foregoing type have, in addition to the counterweights which are secured on the crankshaft, additional balancing weights which are driven by the crankshaft and rotate oppositely to one another in order to achieve a balance of the reciprocating free mass forces. Such balancing weights are generally arranged below or laterally of the crankshaft in order to keep their path of movement outside of the paths of movement of the crankshaft and the connecting rod.
The arrangement of the balancing weights below the crankshaft requires a lower placement of the crankcase so that the balancing weights do not dip into the lubricating oil provided there. This arrangement is disadvantageous, due to the resulting size increase of the engine. Also, the drive chain which drives the balancing weights is complicated by the lower placement.
The arrangement of the balancing weights laterally of the crankshaft leads automatically to a considerable broadening of the crankcase and thus is also disadvantageous because of the resulting increase in engine size.
Arrangements have also been suggested which use balancing weights which rotate around the crankshaft connecting-rod bearing pin. Such balancing arrangements are, however, particularly complicated in their structure and furthermore require a considerable extension of the crankshaft or its connecting-rod bearing pin in an axial direction, which again is very disadvantageous.